Victoria's regional rail operator V/Line has an overcrowding problem, and the statistics show it is not going away, even as it adds 16 extra three-carriage trains to its fleet.

James Pinder, V/Line's CEO, admitted in state parliament on Thursday that as quickly as its manufacturer Bombardier builds a new VLocity train, new passengers fill it.

"We're adding one train a month, one train every six weeks to our fleet, but that capacity gets absorbed very quickly," Mr Pinder said.

V/Line publishes new figures each month that show which of its peak-hour services are at 100 per cent capacity or more. March's numbers reveal standing room-only has become the new normal for many commuters.

On the Geelong line, V/Line's busiest, 12 of 16 morning peak trains are more than 100 per cent full well before they reach Southern Cross Station.

This includes the first train of the day, the 4.32am from Waurn Ponds, which is standing room only by the time it departs Tarneit station in Melbourne's outer west at 5.19am.

The Gippsland line has four trains that reach Melbourne before 9am, two of which were at 100 per cent capacity last month, and three trains that depart Melbourne for Traralgon between 4pm and 6pm, two of which were standing room only for much of the journey.

The Andrews government allocated three new carriages to two peak-hour Gippsland services this month to address the problem.

Crowding on Bendigo and Seymour line trains is less problematic, V/Line figures show.

At the parliamentary inquiry, Mr Pinder suggested crowded carriages were less a growth phase than a permanent change in character from regional to commuter belt service for V/Line's busiest lines.

"Standing on V/Line trains is not something that Victorians are used to," he said.

"Our railway and our region and our state is changing. More and more people are coming to live in Victoria, our network is carrying more and more people and we are on a transformational journey.

"Do we like the fact that on some of our trains on some stations within that corridor, people have to stand for 20 minutes? No, but ... we are in some ways victims of our own success."

Jeroen Weimar, Public Transport Victoria's chief executive, told the inquiry regional rail patronage was growing faster than any other mode in the state, including trams and metropolitan trains.

"We are seeing a level of ridership on the network that we really have not seen before," Mr Weimar said.

Meanwhile, Ms Bordonaro has taken to heading across the CBD to Southern Cross Station for a Gippsland-bound train in the evening, to ensure she gets a seat and doesn't have to stand all the way to Pakenham. Sometimes all seats are occupied before the train reaches Flinders Street Station.

Having to stand all the way to Gippsland means much more than tired feet, she says. It is a drain on productivity and even quality of life.

"There's this idyllic dream that is sold to a lot of people; move to a regional area and you could commute in an hour and work or read while you travel, but it's really hard to work on your laptop if you're standing."